Dr Kent Brantly and Nancy Writebol are the first Americans to be evacuated from Africa with the virus. Photo: AFP

Authorities decided to place him in isolation as a precaution, though there had been no official diagnosis and there were other diseases that could have caused his symptoms, said Eileen de Villa, an official with the region’s public health office.

As well as quarantining the patient, the hospital had enacted other precautionary measures, she said.

Advertisement

US doctor Kent Brantly, who was brought back from Liberia after being infected with Ebola, said he was getting better.

‘‘I am growing stronger every day, and I thank God for his mercy as I have wrestled with this terrible disease,’’ he said in a statement released by Samaritan’s Purse, the international Christian humanitarian organisation he was working for in Liberia.

Dr Brantly was flown back to the US last week from Africa in an air ambulance to be treated for the deadly virus, making him the first Ebola patient in the US.

‘‘I am writing this update from my isolation room at Emory University Hospital [in Atlanta], where the doctors and nurses are providing the very best care possible,’’ the 33-year-old physician said.

Also hospitalised in isolation at Emory is Nancy Writebol, who was infected with Ebola at the same medical centre where Dr Brantly worked in Liberia.

The condition of both patients improved after they were given an experimental serum, never before used on humans, before travelling to the US.

Spokesmen for two key aid groups said the international response to the Ebola outbreak had been slow and inadequate, and the World Health Organisation was at least partly to blame.

On Friday, the Geneva-based organisation designated the outbreak as an international public health emergency, eight months after it began. On May 18, when the situation seemed to be stabilising, the WHO predicted in a statement that the outbreak "could be declared over on May 22".

The WHO's leaders "need to do a reality check and step up", Koen Henckaerts, a health expert with the European Commission's humanitarian aid division, said in a telephone interview from the Liberian capital of Monrovia. "There is a lack of co-ordination among all the different partners."

It's the first time Ebola has appeared in West Africa. A lack of border controls has allowed infected people who didn't seek medical care because of fear, suspicion or stigma to travel freely between countries. Unsanitary funeral practices involving contact with corpses have also fanned the spread.

Part of the problem is weak leadership by health ministries in the affected countries, which have never faced the disease and need help with hands-on management, Mr Henckaerts said, calling for more WHO involvement.

"The WHO has a big responsibility to do more than just give technical advice," he said.

Doctors Without Borders, with almost 700 workers in the affected region, also was critical, saying in a statement that it has been repeating for weeks that "a massive medical, epidemiological and public health response is desperately needed to save lives and reverse the course of the epidemic."

Lives are being lost, the doctors' group said, because the response is too slow.

The outbreak has killed 961 people in Guinea, Liberia, Nigeria and Sierra Leone since it was first reported, with 68 new cases reported over two days, the WHO said yesterday.

Nigerian President Goodluck Jonathan declared a national emergency on Friday, several hours after the WHO called the epidemic a global health crisis.

"We try to exert the degree of leadership which is necessary for the situation," Keiji Fukuda, WHO's assistant director-general, said on Friday in Geneva. "At the same time, we always respect the sovereignty of countries. We don't see ourselves as a policeman just saying, 'Do this, do that.' "

In May, after the WHO predicted the outbreak's close, staff members from several international health groups left the region. Rather than ending, however, there may just have been a lull in cases as infections went unreported, causing the epidemic to reignite and worsen in Sierra Leone and Liberia, said Stephan Monroe, the deputy director of the US Centres for Disease Control's National Centre for Emerging and Zoonotic Infectious Diseases.

"In hindsight, the collective we - that is, the international response - should have made sure the fire was entirely out," Mr Monroe said.

The World Health Organisation has scheduled an August 11 panel of medical ethicists to explore the use of experimental treatments for Ebola, after an experimental antibody cocktail developed by San Diego-based Mapp Biopharmaceutical was used to treat Dr Brantly and Ms Writebol.

It remains unclear if they were helped by Mapp's treatment, which has been dubbed ZMapp. More than 40 per cent of people infected by the virus have survived in this outbreak, probably because of early medical care, health officials say.